Salinization and origin of the coastal shallow groundwater aquifer, northwestern nile delta, Egypt

Abstract

Serious salinization problem is affecting the northern Nile Delta basin and its groundwater aquifers. The hydrochemistry of major ions (K+, Na+, Mg+, Ca2+, Cl−, SO42−, HCO3−, CO32−) and the trace elements (Fe, Mn, Zn, Pb, Cd, Cr, Cu, Ni) have been used to constrain the hydrochemical characteristics, source, and salinization processes of the shallow coastal aquifer, northwestern Nile Delta. Twenty groundwater wells, varying in depth from 17 to 40 m, had been examined and sampled to carry out the physicochemical parameters and chemical compositions of the groundwater and to obtain additional information on the possible contamination with major elements, trace elements (heavy metals), and nutrients (NH4+, NO3−, PO42−). The hydrochemical data indicated that the groundwater of the coastal aquifer, northwestern Nile Delta, is meteoric in origin and is mixed with marine water. The coastal plain aquifer is recognized to be at high risk of increasing salinization. The salinity of the groundwater as a total dissolved solid (TDS) ranges from 1,288 to 4,907 mg/l with an average of 3,155 mg/l. The electric conductivity (EC) of the groundwater ranges from 1,900 to 9,790 μS/cm with an average of 4,620 μS/cm. It is directly related to TDS and the geographical position of each well. The groundwater is slightly alkaline with pH ranges from 7.01 to 8.2. The high salinity, pH, and EC values support the conclusion of seawater intrusion. The nutrient content such as nitrates is higher than the standard values, which mainly resulted from rural sources. The concentrations of the trace elements are lower than the standard values except for iron, manganese, and nickel. This groundwater can be used for crop irrigation but must be treated before using for drinking.